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The development of polysaccharide drugs requires a thorough understanding of their quantitative and pharmacokinetic properties. However, the complexity of biological samples presents a challenge for direct analysis using UHPLC-QTOF MS. Therefore, it is essential to establish a method for the selective enrichment of polysaccharides. In this study, we developed an efficient method for the quantitative determination of polysaccharides by integrating magnetic molecularly imprinted polymers (MIPs) for sample pretreatment and UHPLC-QTOF MS for analysis. The MIPs were prepared using molecularly imprinted and boric acid affinity technologies, which combined the advantages of specific recognition and reversible binding to polysaccharides. The MIPs exhibited high dispersibility and uniform particle size, and adsorption experiments demonstrated their specific recognition of BG136, a polysaccharide with immunological activity. The proposed method was used for the purification and enrichment of BG136 in plasma with recoveries between 91.29% and 113.03%. This simple method demonstrated high selectivity, fast separation, and satisfactory recoveries providing an approach for polysaccharide determination with UHPLC-QTOF MS. [ABSTRACT FROM AUTHOR]

Aminoglycoside antibiotics exhibit broad-spectrum antibacterial activity, good efficacy, and stability. However, due to the emergence of antibiotic resistance, their use as broad-spectrum antibiotics is restricted. Bacteria producing the bifunctional enzyme, 6′-aminoglycoside acetyltransferase 2″-aminoglycoside phosphotransferase [AAC(6′)-APH(2″)], can modify aminoglycoside antibiotics, leading to the emergence of clinical drug resistance. A method based on ultra-high performance liquid chromatography–mass spectrometry (UHPLC-MS) is reported to monitor the modification of aminoglycoside antibiotics and to screen potential inhibitors of AAC(6′)-APH(2″) from marine natural products. Instead of using purified AAC(6′)-APH(2″), Escherichia coli cells harboring AAC(6′)-APH(2″) were employed. In vivo enzyme assays, conducted in the physiological environment, compensated for the disparity between in vitro responses and those in living cells. The inhibition zone method was used to verify the reliability of the UHPLC-MS results. From a library of 63 marine natural products, Mer-C-3 and Mer-c-8e pyridine alkaloids were shown to provide inhibitory activity against AAC(6′)-APH(2″) in living bacteria. The UHPLC-MS-based approach offers improved speed, convenience, and sensitivity compared with the traditional inhibition zone assay for the screening of enzyme inhibitors. [ABSTRACT FROM AUTHOR]